1. The Field of the Invention
The invention is directed to a non-contact gauging apparatus and, more specifically, to a method for performing surface profiling of a workpiece.
2. The Background Art
Cylindrical workpieces are used throughout manufacturing to operate in rotating machinery such as assembly line machinery or in turbines used in power generation or propulsion. Such workpieces may have the shape of a cylinder or cone, or have circularly symmetric parts of irregular axial cross section. A workpiece may have a crown portion, a concave portion, or a multiplicity of both. Workpieces range in sizes from two inches in diameter to several feet in diameter depending on the function or application of the workpiece.
For quality control and assessment, accurate measurements of the workpiece provide information about the dimensions. During use, the workpiece may undergo wear and strain that alters its dimensions in order to ensure quality performance, it is necessary to periodically take accurate measurements of the workpieces. It is further necessary to perform diameter measurements before machining a workpiece in order to accurately apply a grinding wheel to obtain the target diameters. After the machining process it is desirable to measure the shape of the workpiece as a record and to ensure quality control of the process.
Diameter measurements have been conventionally performed through the use of micrometers or calipers that encircle the workpiece so as to come into contact with opposing side surfaces. This process is difficult and time consuming and requires the expertise of a skilled operator performing the measurement. Since mechanical surface contact is required for micrometers and calipers to work, slight fluctuations in surface texture introduce error in measurement. The contours of the workpiece may make contact gauging instruments impossible to use due to the lack of positive engagement between the contacting surfaces of the instruments with the workpieces. A further disadvantage is that contact with the workpiece creates undue wear on the workpiece which cause deformities in the workpiece.
More sophisticated measurement methods introduce the use of non-contact gauging by measuring the intensity of light reflected from a workpiece surface. Such a non-contact system is disclosed in U.S. Pat. No. 6,062,948 to Schiff et al. which is hereby incorporated by reference. Non-contact gauging systems are effective in determining a diameter at a position along a longitudinal axis of the workpiece.
In order to better ascertain the dimensions of a workpiece, it is desirable to obtain the entire profile of a workpiece. Profiling requires numerous diameter measurements along the longitudinal length of the workpiece. The more diameter measurements that are performed, the more accurate the profile of the workpiece will be. Conventional methods require that the measuring equipment be positioned at various locations along a longitudinal axis for each diameter measurement. Thus, with even non-contact gauging systems, profiling a workpiece is time consuming, repetitive, and subject to operator error.
It would be an advancement in the art to provide a non-contact gauging system that efficiently, expeditiously, and accurately profiles a workpiece surface. It would be a further advancement to provide such a system that provides an operator interface that is easily understood. Such a system and method are disclosed herein.
The invention is directed towards a non-contact gauging system and method to profile a workpiece. The system includes a sensor head having a light source and a detector for receiving and determining the intensity of a portion of reflected light. A non-contact sensor enjoys the benefits of increased speed in measuring, superior accuracy, and reduced wear on the workpiece. The sensor head couples to a sensor arm that is movable in longitudinal, lateral, and transverse directions.
The system further includes a computer having a processor and a memory with instruction code. The computer is in communication with the sensor head and the sensor arm to control their operation. The memory includes a sensor arm module to control movement of the sensor arm and a sensor head module to control operation of the sensor head. The memory further includes a wireframe module that determines the diameters of the workpiece and generates a workpiece profile.
The sensor arm and sensor head modules direct the sensor arm and sensor head to perform proximity measurements of the workpiece surface. The proximity measurements are made along at least three parallel, lateral tracks that extend along a longitudinal length of the workpiece surface. The sensor head takes proximity measurements as it is moved continuously along each lateral track. During movement, the sensor head directs a beam of light to the workpiece surface and measures the intensity of reflected light to determine the proximity.
The sensor head sends signals indicative of the proximity measurements to the computer. The wireframe module determines the diameters of the workpiece along the longitudinal length based on the proximity measurements and generates a workpiece profile. Based on the proximity of the sensor to the workpiece at various lateral positions, the computer performs geometrical calculations to determine the diameter at a longitudinal position. Determining diameters of the workpiece along the longitudinal length of the workpiece allows the computer to determine a profile of the workpiece.